Concentric Motor Control Circuit Reduces Impedance
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Solution Overview
Problem
Existing electric power steering systems face issues with increased impedance across the three-phase bridge circuit due to the placement of semiconductor devices and electrolytic capacitors, poor heat dissipation, and inefficient mounting of the control board, leading to reduced power efficiency and difficulty in aligning bus bars.
Innovation Solution
The electric driving device configures semiconductor switching devices and capacitors in pairs for each arm of the three-phase bridge circuit, disposed concentrically with the rotor shaft, and incorporates a heat sink to enhance heat dissipation, while using high thermal conductive materials and resin molding to reduce internal impedance and improve mounting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control device is disposed on the axis line of the rotor shaft or on the bracket of the electric motor with power boards integrated and electrolytic capacitors gathered at one point, then the device structure is simplified, but the impedance between the bridge circuit and capacitors increases
Solution Approach 1:
The power boards are divided into multiple separate boards instead of being integrated into a single board. The electrolytic capacitors are distributed to each power board rather than being gathered at one point. This segmentation reduces the impedance between the bridge circuit and capacitors while maintaining a simplified overall device structure.
Solution Approach 2:
Each power board is equipped with its own electrolytic capacitors locally, rather than having all capacitors centralized. This local quality approach reduces the impedance in each local circuit while maintaining the simplified device structure.
2Device complexity
If heat from the coil and electrolytic capacitors is released into the space within the ECU case, then the heat dissipation path is simplified, but the heat dissipation effect becomes poor
Solution Approach 1:
The heating components (coil and electrolytic capacitors) are extracted from the ECU case and disposed outside of it. This extraction allows for more effective heat dissipation paths while simplifying the heat dissipation structure by removing the constraint of releasing heat into the confined ECU space.
Solution Approach 2:
The heat dissipation is moved from the confined three-dimensional space within the ECU case to the external environment, providing additional dimensional space for heat dissipation and improving the overall heat dissipation effect.
3Device complexity
If the power portion and control portion are connected by disposing terminals in a row, then the connection structure is simplified, but the mounting efficiency of the control board deteriorates
Solution Approach 1:
The terminals are segmented and disposed in different locations rather than being arranged in a single row. This segmentation allows for more flexible mounting arrangements that improve control board mounting efficiency while maintaining a simplified connection structure.
Solution Approach 2:
The terminal arrangement transitions from a one-dimensional row configuration to a two-dimensional distributed configuration across different locations on the control board, improving mounting efficiency while keeping the connection structure simplified.
4Ease of manufacture
If bus bars are used to form the power line with resin molding, then the manufacturing process is simplified, but the bus bars cannot be aligned parallel to each other
Solution Approach 1:
The bus bars are segmented into multiple separate pieces rather than being formed as a single integrated structure. This segmentation allows each bus bar to be independently aligned parallel to each other while maintaining the simplified resin molding manufacturing process.
Solution Approach 2:
Each bus bar segment is locally positioned and aligned parallel to the others, ensuring proper alignment while maintaining the simplified manufacturing process through resin molding.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces impedance across the three-phase bridge circuit, enhances power efficiency, and improves heat dissipation, allowing for efficient ripple absorption and electromagnetic noise reduction, thereby improving the overall performance of the electric power steering system.
Implementation Method 1
it is necessary to release heat from the heating portion using the heat sink built in the ECU
Implementation Method 2
using high thermal conductive materials to reduce internal impedance and improve mounting efficiency
Data Source
Figure 1
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Figure 3
AI summary
A control device (3) controlling an electric motor (2) is disposed on an axial line of a rotor shaft (30) of the electric motor (2). The control device (3) includes semiconductor switching devices (15) forming a three-phase bridge circuit that controls a current of the electric motor (2) and capacitors (13) that suppresses a ripple component of a current flowing to the electric motor (2). The semiconductor switching devices (15) and the capacitors (13) are provided in pairs for respective arms of the three-phase bridge circuit and disposed concentrically. Hence, impedance across the three-phase circuit controlling a current flowing to the electric motor is reduced. Consequently, not only can ripples be absorbed efficiently but also power efficiency of a driving device can be enhanced.